The present invention relates to elastic shaft couplings which provide for damping of fluctuations in the rotational velocity of the driving shaft.
According to German Offenlegungsschrift No. 24,44,787 and German Pat. No. 30 33 302 A 1, couplings are known in which radially-directed sets of leaf springs are positioned between a primary part and a secondary part and are gripped by intermediate elements. Between the elements, for the purpose of damping, are situated oil-filled chambers. The oil, upon application of a load, is forced from one chamber to the other. U.S. Pat. No. 2,513,379 discloses a coupling in which helical springs, tangentially directed in circumferential direction to the axis of rotation of the coupling are partially surrounded by cup-like casings. The casings can be slipped into one another and define aperatures through which damping oil flows. These constructions are limited in that they permit only slight angular deflections between the primary part and secondary part and, additionally are very complicated in structure.
German Pat. No. 3,228,673 A 1 discloses a rotary oscillation damper intended for use in vehicle friction-clutch couplings, in which the transmission of torque from the drive shaft to the somewhat drumlike secondary part carried by the shaft is accomplished by means of a ring-shaped coupling body, disposed in the secondary part. The coupling body engages the drive shaft with a thrust device which permits longitudinal displacement and is displaceably connected to the periphery of the secondary part by means of an axial tooth construction. Cup springs, supported on the wall of the secondary part, are situated on both sides of the coupling body. The chambers on both sides of the springs are filled with damping oil, which, upon application of a load, can flow over from one chamber into the other through a throttle channel located in the coupling body. When the driving primary part moves in one direction of rotation or the other, the coupling body comes to lie against one cup spring or the other as a result of the variable axial thrust. The overflowing oil carries along the damped secondary part.
This sort of arrangement and manner of loading the springs makes possible greater angular deflections between the primary and secondary parts than in the case of other prior couplings. This construction is disadvantageous in several respects, however. First, only one cup spring is used in each direction of rotation. The other remains non-participating. This must be regarded as poor utilization of the existing spring volume, adding substantial cost to the coupling construction. The variable stresses on the springs when the direction of rotation is reversed also cause considerable pre-stressing of the springs, which must be greater than the operating stress, whereby further limits are placed on the area of effective rotation. Furthermore, it must be regarded as disadvantageous that, as a result of the immediate proximity of the coupling body to the cup springs, contaminated damping oil can get on the thrust device as a result of wear. This can lead to premature wear on the thrust device and thereby to shortening of the life span of the coupling.
Fundamentally, coupling members whose inclined surfaces lie tangential to the axis of rotation, as in the case of the aforementioned German patent, have the disadvantage of a torsional play which cannot be eliminated, by means of which velocity impacts are generated when the direction of rotation is reversed. Such impacts can have a very deleterious effect on the coupling and the machines to which it is attached. Also, with time, due to the gradual weakening of the springs, there occurs an increase in the torsional play, which can only be eliminated by inserting new springs in a time consuming operation. The shut down time may be unpermissibly long in some instances.
The problem forming the basis of the invention is the creation of a high-rotary-elastic shaft coupling with fluid damping or dash-pot action in which the above-mentioned disadvantages are avoided and which has a high specific transmitting capacity; and in which the transmitting mechanism, which converts the tangential movement of the primary part into an axial movement and thence again into a tangential movement of the secondary part, is free from play; and which fully utilizes the total spring volume independently of the direction of moment.
Additionally, depending on the instances of application and conditions of operation, the damping behavior of a high-rotation-elastic coupling can be controlled according to the present invention with fluid damping. Thus there can be the requirement that the fluid damping should increase with increasing moment of rotation, or that greater damping be provided in passing through zero, that is, when the rotational force moment is zero. Furthermore, in the case of installations heavily prone to oscillation or vibration, there is the desire to alter the damping additionally.